In some cases, wireless microphones are used on a stage. Plural performers who work on stage carry portable wireless microphones. Voices emitted from the performers are received by the microphones and loud sound waves are emitted from a loudspeaker installed on the stage.
A radio wave from the wireless microphone carried by each performer is sent to the corresponding receiver. The radio wave is not always received in good condition by the receiver. For instance, an operator A that monitors a procedure of performance on the stage while manipulating a mixing console may notice that the radio wave from the wireless microphone of one performer is not received in good condition by the receiver. In that case, the operator A must instruct another operator (operator B) who is on backstage to check or maintain the wireless microphone. To this end, the operator A provides an instruction to the operator B on backstage by using an intercom system or the like within that hall.
Such a method will not arise a severe problem when a communication system using wireless microphones is small-scaled and operators are few. On the other hand, a number problems will arise when a communication system using wireless microphones is large-scaled and operators are many. For example, an instruction from a main operator to another operator may become intricate, or otherwise the main operator is unable to confirm that another operator conducted as instructed by the main operator. These problems may be due to the fact that all the operators have difficulty in equally recognizing a condition of the communication system using the wireless microphones.
When the instruction is communicated from one operator to another by voice, they are unable to emit a large voice, for example, during the performance. It may be difficult to correctly determine who has provided the instruction.
When the intercom system is wireless, interference between the intercom system and the microphone system may occur.
Transmitters of wireless microphones for use on stage are in some cases embedded in, for example, clothes of performers. For each maintenance or each initial setting of the transmitters, it becomes necessary to take out the microphones from the clothes in order to operate operation portions of the transmitters of the wireless microphones. In many cases, maintenance and initial setting may be difficult.
For example, Japanese Laid-Open Patent Application Publication No. 2002-119774 discloses a wireless operating system for stage apparatuses. But, the system disclosed therein is incapable of solving the above mentioned problems.